Neurodegenerative diseases include several kinds of pathologies causing versatile diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), dementia with Lewy body (DLB), and frontotemporal dementia (FTD), etc. Due to different causes, these diseases may develop various impaired clearance of biomolecules, which are regarded as biomarkers with these diseases. For example, β-amyloid (Aβ), tau protein and their derivates are typically related to AD, while α-synuclein and its derivates are representative biomarkers for PD and DLB. It is suggested to discriminate patients by assaying the typical biomarkers. For example, AD patients show higher values for the product in concentrations of plasma Aβ1-42 and tau protein, denoted as ϕAβ1-42×ϕtau, as compared to that of normal controls (NC, or referred as to healthy subjects) and DLB patients, as shown in FIG. 1A. But, in FIG. 1A, DLB patients will be miss-diagnosed as normal controls. As the plasma α-synuclein is assayed for NC, DLB patients, and AD patients, patients with DLB show higher concentrations of plasma α-synuclein, denoted as ϕα-syn, as compared to NC, as shown in FIG. 1B. However, some AD patients also show the same levels of plasma α-synuclein as DLB patients. Thus, DLB patients can not be well discriminated from AD patients by merely assaying ϕα-syn. According to results in FIGS. 1A and 1B, DLB patients can not be accurately diagnosed by assaying either of plasma ϕAβ1-42×ϕtau or plasma ϕα-syn.